In the second half of his life, Max Planck concerned himself increasingly with philosophical and ideological issues of modern science. There is a close link between both these areas: Planck constantly labored to expose fundamental correlations, ever in search of absolute truths. With his philosophical contemplations of the world, he wanted to offer an adequate contribution toward a coherent physical worldview.

Particularly in the last decades of his life, Planck made an effort to transmit the findings of modern science to the general public. This stemmed from Planck's basic convictions about the cultural value of science for mankind-a typical attitude for Planck's generation. He wrote articles for daily newspapers and popular science magazines, gave interviews, and broadcast speeches on radio. But the public lecture became his preferred forum. He went on extended lecture tours throughout Germany and abroad until the year he died. He himself pointed out one motivation for such a busy lecturing schedule: "At my age of 89 I cannot be productive in science anymore: what remains for me is the possibility of reaching out to people in their search for truth and insight, above all young people."

"It is certain that Planck did not believe in any specific form of religion; but he was religious (in the sense of Spinoza and Goethe) and repeatedly pointed it out. And since he was one of the most truthful of persons, there must have been a profound feeling behind his words that was a strong aid to him in the tragic vicissitudes of his life."
Lise Meitner, 1958

Planck's response to an inquiry about his attitude toward religion:
"I have always been deeply religiously disposed, but I do not believe in a personal God, not to mention a Christian God. You would find more about this in my essay on 'religion and science'."